1. 得到系统中soft dog的信息
# modinfo softdog
filename: /lib/modules/3.2.0-4-686-pae/kernel/drivers/watchdog/softdog.ko
2. 加载模块
# insmod /lib/modules/3.2.0-4-686-pae/kernel/drivers/watchdog/softdog.ko
3. 此刻可见/dev/watchdog, 或创建
# mknod /dev/watchdog c 10 130
4. 查看dev并赋予权限
# ls -l /dev/watchdog
crw------- 1 root root 10, 130 Mar 21 16:27 /dev/watchdog# chmod o+rw /dev/watchdog
5. 测试使用watch dog
简单可写为：
# echo 0 > /dev/watchdog ///从此刻起计时，启用watchdog
# echo -n V > /dev/watchdog ///停用watchdog
6. 硬件与软件watchdog的区别
硬件watchdog必须有硬件电路支持, 设备节点/dev/watchdog对应着真实的物理设备， 不同类型的硬件watchdog设备由相应的硬件驱动管理。软件watchdog由一内核模块softdog.ko 通过定时器机制实现，/dev/watchdog并不对应着真实的物理设备，只是为应用提供了一个与操作硬件watchdog相同的接口。
硬件watchdog比软件watchdog有更好的可靠性。 软件watchdog基于内核的定时器实现，当内核或中断出现异常时，软件watchdog将会失效。而硬件watchdog由自身的硬件电路控制, 独立于内核。无论当前系统状态如何，硬件watchdog在设定的时间间隔内没有被执行写操作，仍会重新启动系统
看门狗是混杂设备，所以主设备号是10，/include/linux/miscdevice.h 中定义他的次设备号为130
1 #include <stdio.h>
2 #include <stdlib.h>
3 #include <unistd.h>
4
5 #include <sys/types.h>
6 #include <sys/stat.h>
7 #include <fcntl.h>
8 #include <termios.h>
9 #include <errno.h>
10 #include <signal.h>
11 #include <time.h>
12 #include <pthread.h>
13 #include <sys/time.h>
14 #include <linux/watchdog.h>
15 #include <sys/ioctl.h>
16
17 time_t backTime;
18 struct tm *pBackTime;
19 int wt_fd;
20
21 static void sigAlarm(int sig)
22 {
23 char flag = ‘0‘;
24 (void)time(&backTime);
25 pBackTime= localtime(&backTime);
26 printf("day: %d; hour: %d; min: %d; sec: %d\n", pBackTime->tm_mday, pBackTime->tm_hour, pBackTime->tm_min, pBackTime->tm_sec);
27
28 write(wt_fd, &flag, 1); //Reset Watchdog 喂狗
29 alarm(2);
30 return;
31 }
32
33
34 int main()
35 {
36 char flag = ‘V‘;
37 int ret;
38 int timeout = 42;
39
40 if(SIG_ERR == signal(SIGALRM, sigAlarm))
41 {
42 perror("signal (SIGALARM) error");
43 }
44
45 wt_fd = open("/dev/watchdog", O_RDWR);
46 if(wt_fd <= 0)
47 {
48 printf("Fail to open watchdog device!\n");
49 }
50 else
51 {
52 write(wt_fd,NULL,0);
53 printf("Turn on Watch Dog\n");
54 ret = ioctl(wt_fd, WDIOC_SETTIMEOUT, &timeout);
55 if(EINVAL == ret)
56 {
57 printf("EINVAL Returned\n");
58 }
59 else if(EFAULT == ret)
60 {
61 printf("EFAULT Returned\n");
62 }
63 else if(0 == ret)
64 {
65 printf("Set timeout %d secs success\n", timeout);
66 }
67 else
68 {
69 printf("Ret %d\n", ret);
70 }
71 }
72
73 alarm(3);
74
75 while(1);
76
77 write(wt_fd, &flag, 1);
78 printf("Turned off Watch Dog\n");
79 close(wt_fd);
80 return 0;
81 }
http://blog.sina.com.cn/s/blog_69a04cf401016gz4.html